A multirotor [1] or multicopter is a rotorcraft with more than two lift-generating rotors. An advantage of multirotor aircraft is the simpler rotor mechanics required for flight control. Unlike single- and double-rotor helicopters which use complex variable pitch rotors whose pitch varies as the blade rotates for flight stability and control, multirotors often use fixed-pitch blades; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by each.
Due to their ease of both construction and control, multirotor aircraft are frequently used in radio control aircraft and unmanned aerial vehicle (UAV) (drone) projects [2] [3] [4] [5] [6] [7] in which the names tricopter, quadcopter , hexacopter and octocopter are frequently used to refer to 3-, 4-, 6- and 8-rotor rotorcraft, respectively. [8] There is also the X8 (also called octo-quad) configuration that is similar to the quadracopter design, except that it has eight rotors; the lower of which have a reversed rotation direction. [9]
In order to allow more power and stability at reduced weight, coaxial rotors can be employed, in which each arm has two motors, running in opposite directions which cancels out rotational torque (one facing up and one facing down). [11]
Also possible is the addition of horizontal propellers [12] [13] [14] These types of rotorcraft (which have just 4 vertical propellers) are called quadplanes. [15]
A tiltrotor is an aircraft that generates lift and propulsion by way of one or more powered rotors mounted on rotating shafts or nacelles usually at the ends of a fixed wing. Almost all tiltrotors use a transverse rotor design, with a few exceptions that use other multirotor layouts.
A radio-controlled helicopter is model aircraft which is distinct from a RC airplane because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, of which some are more maneuverable than others. The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities.
Helicopter flight controls are used to achieve and maintain controlled aerodynamic helicopter flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a desired way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.
The tail rotor is a smaller rotor mounted vertically or near-vertically at the tail of a traditional single-rotor helicopter, where it rotates to generate a propeller-like horizontal thrust in the same direction as the main rotor's rotation. The tail rotor's position and distance from the helicopter's center of mass allow it to develop enough thrust leverage to counter the reactional torque exerted on the fuselage by the spinning of the main rotor. Without the tail rotor or other anti-torque mechanisms, the helicopter would be constantly spinning in the opposite direction of the main rotor when flying.
A coaxial-rotor aircraft is an aircraft whose rotors are mounted one above the other on concentric shafts, with the same axis of rotation, but turning in opposite directions (contra-rotating).
On a helicopter, the main rotor or rotor system is the combination of several rotary wings with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words helix, helik-, meaning spiral; and pteron meaning wing.
A quadcopter, also called quadrocopter, or quadrotor is a type of helicopter or multicopter that has four rotors.
A gyrodyne is a type of VTOL aircraft with a helicopter rotor-like system that is driven by its engine for takeoff and landing only, and includes one or more conventional propeller or jet engines to provide thrust during cruising flight. During forward flight the rotor is unpowered and free-spinning, like an autogyro, and lift is provided by a combination of the rotor and conventional wings. The gyrodyne is one of a number of similar concepts which attempt to combine helicopter-like low-speed performance with conventional fixed-wing high-speeds, including tiltrotors and tiltwings.
A rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotary wings that spin around a vertical mast to generate lift. The assembly of several rotor blades mounted on a single mast is referred to as a rotor. The International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway.
The Sikorsky X2 is an experimental high-speed compound helicopter with coaxial rotors, developed by Sikorsky Aircraft, that made its first flight in 2008 and was officially retired in 2011.
The Fairey FB-1 Gyrodyne is an experimental British rotorcraft that used single lifting rotor and a tractor propeller mounted on the tip of the starboard stub wing to provide both propulsion and anti-torque reaction.
The Sikorsky S-97 Raider is a high-speed scout and attack compound helicopter based on the Advancing Blade Concept (ABC) with a coaxial rotor system under development by Sikorsky Aircraft. Sikorsky planned to offer it for the United States Army's Armed Aerial Scout program, along with other possible uses. The S-97 made its maiden flight on 22 May 2015.
The Volocopter VC2 is a German single-place experimental electric multirotor personal air vehicle that was built by Volocopter GmbH of Bruchsal, Germany.
ArduPilot is an open source, uncrewed vehicle Autopilot Software Suite, capable of controlling:
Guangzhou EHang Intelligent Technology Co. Ltd. is a company based in Guangzhou, China that develops and manufactures autonomous aerial vehicles (AAVs) and passenger AAVs which have entered service in China for aerial cinematography, photography, emergency response, and survey missions.
Krossblade Aerospace Systems is an aviation company founded in 2014 in Phoenix Arizona, USA. The company is known for developing a 5-seat VTOL concept, SkyCruiser, hybrid vehicle for vertical take-off and landing, and for its drone/UAV prototype, named SkyProwler. Both aircraft employ the switchblade transformation mechanism to transform from a multirotor aircraft for vertical take-off and landing, to a pure winged aircraft, for rapid and efficient cruise.
Urban air mobility (UAM) is the use of small, highly automated aircraft to carry passengers or cargo at lower altitudes in urban and suburban areas which have been developed in response to traffic congestion. It usually refers to existing and emerging technologies such as traditional helicopters, vertical-takeoff-and-landing aircraft (VTOL), electrically propelled vertical-takeoff-and-landing aircraft (eVTOL), and unmanned aerial vehicles (UAVs). These aircraft are characterized by the use of multiple electric-powered rotors or fans for lift and propulsion, along with fly-by-wire systems to control them. Inventors have explored urban air mobility concepts since the early days of powered flight. However, advances in materials, computerized flight controls, batteries and electric motors improved innovation and designs beginning in the late 2010s. Most UAM proponents envision that the aircraft will be owned and operated by professional operators, as with taxis, rather than by private individuals.
The Volocopter 2X is a German two-seat, optionally-piloted, multirotor eVTOL aircraft. The personal air vehicle was designed and produced by Volocopter GmbH of Bruchsal, and first introduced at the AERO Friedrichshafen airshow in 2017. The aircraft is sold complete and ready-to-fly. Volocopter was formerly known as E-volo.
The SureFly is a two-seat hybrid eVTOL aircraft designed by American truck-manufacturer Workhorse Group, before the program was bought by Moog Inc. for $5 million in December 2019.